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The structure of the hydrogenation product of [2.2]metacyclophane
TetxmhedronLetten 100.14,ppll.43- 1146.1973. lw!pwn Prark
Printed
in
hat
Ihi-.
THE STRUCTIJRS OF THE HYDROGENATION PRODUCT OF 12.21METACYCLOPHANE Elieabeth Langer and Harald Lehner Dehrkanzel fur Organische Chemie der UniVeraitPt, A-1090 Wi@n @eoelmd io UK 18 Jamary 1973;acooptedfor publieatioa
22 Fbm
1973)
In 1961, Allinger, Da Rooge and Hermann inveatigated the hydrogenation of [2.7]metacyclophane (&) and assigned to the product obtained (m.p. 174") - more or less tentative1.y- the structure of e dodecahydro[;!.2]metacyclophane Q)?
In the course of our studies on the etereochemiatry of chiral [2.2]meta-
cyclophanes2 we gained evidence that during the hydrogenation of & (with PtOz in acetic acid at 25O and atmospheric pressure) intraanular cyclization between the positions 8 and 16 OC~TIYP to give a hexadecahydropyrener the molecular ion Leak in the mace spectrum of the hydrogenation product appeara at m/e = 218, whereas 2 has a molecular weight of 220; moreover, the fragmentation pattern is ty~~ic!Rl for a perhydropyrene. No olefinic protons were detectable in the WMR spec9~rr..Consequently, the proposed structure 2' is incorrect and haa to be revised.
lY3
1144
No. 14
Furthermore WH have determined the configuration of this hexadecahydropyrene of m.p. 174O - one of the fourteen possible configurational isomers (excluding enantiomers of chiral species) - to correspond to stereoformula g So far, only one isomer (viz. !3,m.p. 103') was dee~:ribfd;its structure had been proposed on the basis of stability arguments deduced from equilibrjum experiments3 . Our assumption in favour of a highly symmetric and rather rigid molecule - based on its high m.p. of 174O - was confirmed by the 13C NMR spectrums the 1H decoupled spectrum exhibits five individual signals consistent with either Gzv or czh symmetry. The following structures are in accord with these symmetry requirements8 2 and 2 (sSv) or 2 and i (E2h).
The final assignment of the correct configuration i was established b:r 1H NMR studies at 100 MHz comparing the spectra of the perhgdroproduct and of a selectively deuterated hydropyrene was obtained from
(a+
positions 3a, 5a, Ra end lea) whit:
[2.2]metacyclophane (I.)by catalytic "hydrogenationtlin a
deuterium atmosphere:
190.14
lU5
1. The protons at C-4, C-5 and C-9, C-10, reap., give rise to a partial spectrum of the AA'BB' type, just weakly perturbed by the protons at C-3s. C-5a and C-83, C-lOa, reap., which Implies a dihedral angle of appr. 60 deg. 2. The same holds for the dihedral angle between these protons and those at C-lob and C-lOc, reap.: the sharp singlet (protons at-C-lob and C-10~) in the spectrum of the deuterated compound becomes slightly broadened in the hydrogenated product LT 6 .
The perhydropyrene &is
made up of four fused cyclohexane rings in the
chair conformation. A very remarkable feature of the hydrogenation of & to 6 is the preservation of symmetry (g2h) aa well as of topology. Detailed papers on the deuteration experiments, the mechanism of the catalytic hydrogenation of & (including the structures of partially hydrogenated intermediates) as well as on the NMB analysis of 6 are in preparation. ACKNOWLEDGEMENTS The authors are greatly indebted to Prof. Dr. K. Schlijglfor helpful advice and for his interest in this work and to Doz. Dr. B. Falk for stimulating diacussions. We are grateful to Dr. A. Hochrainer, Elektrochemie Turgi, for supplying deuterium, to Dr. E.Bretsch, E.T.H. Zurich, for the 13C NMH ape&rum
llq6
No. 14
to Dr. G. Schulz, SANDOZ-Forschungsinstitut Wien,
and to Dr. U. Wagner,
Universitgt Wien, for the 'H NMR measurements.
REFERENCES 1. N-.L.Allinger, M.A. Da Rooge and R.B. Hermann, J. Amer.Chem.Soc. 2,
1974
(1961); cf. also I F. Vijgtleand P. Neumann, Angew.Chem. 84, 75 (197.2); B. H. Smith, "Bridged Aromatic Compounds", p. 249. Academic Press, New York (1964). 2. B. Kainradl, E. Langer, H. Lehner and K. Schliigl,Liebigs Ann.Chem.,in press;
E. Langer and H. Lehner, Monatsh.Chem., in press.
3. K. Smeykal and G. Zimmermann, J.prakt.Chem. 2,
105
(1962).
Printed
in
hat
Ihi-.
THE STRUCTIJRS OF THE HYDROGENATION PRODUCT OF 12.21METACYCLOPHANE Elieabeth Langer and Harald Lehner Dehrkanzel fur Organische Chemie der UniVeraitPt, A-1090 Wi@n @eoelmd io UK 18 Jamary 1973;acooptedfor publieatioa
22 Fbm
1973)
In 1961, Allinger, Da Rooge and Hermann inveatigated the hydrogenation of [2.7]metacyclophane (&) and assigned to the product obtained (m.p. 174") - more or less tentative1.y- the structure of e dodecahydro[;!.2]metacyclophane Q)?
In the course of our studies on the etereochemiatry of chiral [2.2]meta-
cyclophanes2 we gained evidence that during the hydrogenation of & (with PtOz in acetic acid at 25O and atmospheric pressure) intraanular cyclization between the positions 8 and 16 OC~TIYP to give a hexadecahydropyrener the molecular ion Leak in the mace spectrum of the hydrogenation product appeara at m/e = 218, whereas 2 has a molecular weight of 220; moreover, the fragmentation pattern is ty~~ic!Rl for a perhydropyrene. No olefinic protons were detectable in the WMR spec9~rr..Consequently, the proposed structure 2' is incorrect and haa to be revised.
lY3
1144
No. 14
Furthermore WH have determined the configuration of this hexadecahydropyrene of m.p. 174O - one of the fourteen possible configurational isomers (excluding enantiomers of chiral species) - to correspond to stereoformula g So far, only one isomer (viz. !3,m.p. 103') was dee~:ribfd;its structure had been proposed on the basis of stability arguments deduced from equilibrjum experiments3 . Our assumption in favour of a highly symmetric and rather rigid molecule - based on its high m.p. of 174O - was confirmed by the 13C NMR spectrums the 1H decoupled spectrum exhibits five individual signals consistent with either Gzv or czh symmetry. The following structures are in accord with these symmetry requirements8 2 and 2 (sSv) or 2 and i (E2h).
The final assignment of the correct configuration i was established b:r 1H NMR studies at 100 MHz comparing the spectra of the perhgdroproduct and of a selectively deuterated hydropyrene was obtained from
(a+
positions 3a, 5a, Ra end lea) whit:
[2.2]metacyclophane (I.)by catalytic "hydrogenationtlin a
deuterium atmosphere:
190.14
lU5
1. The protons at C-4, C-5 and C-9, C-10, reap., give rise to a partial spectrum of the AA'BB' type, just weakly perturbed by the protons at C-3s. C-5a and C-83, C-lOa, reap., which Implies a dihedral angle of appr. 60 deg. 2. The same holds for the dihedral angle between these protons and those at C-lob and C-lOc, reap.: the sharp singlet (protons at-C-lob and C-10~) in the spectrum of the deuterated compound becomes slightly broadened in the hydrogenated product LT 6 .
The perhydropyrene &is
made up of four fused cyclohexane rings in the
chair conformation. A very remarkable feature of the hydrogenation of & to 6 is the preservation of symmetry (g2h) aa well as of topology. Detailed papers on the deuteration experiments, the mechanism of the catalytic hydrogenation of & (including the structures of partially hydrogenated intermediates) as well as on the NMB analysis of 6 are in preparation. ACKNOWLEDGEMENTS The authors are greatly indebted to Prof. Dr. K. Schlijglfor helpful advice and for his interest in this work and to Doz. Dr. B. Falk for stimulating diacussions. We are grateful to Dr. A. Hochrainer, Elektrochemie Turgi, for supplying deuterium, to Dr. E.Bretsch, E.T.H. Zurich, for the 13C NMH ape&rum
llq6
No. 14
to Dr. G. Schulz, SANDOZ-Forschungsinstitut Wien,
and to Dr. U. Wagner,
Universitgt Wien, for the 'H NMR measurements.
REFERENCES 1. N-.L.Allinger, M.A. Da Rooge and R.B. Hermann, J. Amer.Chem.Soc. 2,
1974
(1961); cf. also I F. Vijgtleand P. Neumann, Angew.Chem. 84, 75 (197.2); B. H. Smith, "Bridged Aromatic Compounds", p. 249. Academic Press, New York (1964). 2. B. Kainradl, E. Langer, H. Lehner and K. Schliigl,Liebigs Ann.Chem.,in press;
E. Langer and H. Lehner, Monatsh.Chem., in press.
3. K. Smeykal and G. Zimmermann, J.prakt.Chem. 2,
105
(1962).